Disconnect the fuel line to the rear bowl. Undo the three screws that hold the bowl cover on, and carefully lift it straight up, so as not to break the thin gasket underneath.

Using needle nosed pliers, bend the metal arm of the float just on the float side of where it contacts the valve, so the float moves away from the cover. It shouldn't take very much.

Reassemble and try it...

I wouldn't be annoyed at the carb rebuilder. it's one of those finicky things that may take a bit of trial and error to get set just right.